致命錯誤：調用一個成員函數的getElementsByTagName（）上的空

Question

if ($rows->length > 0) 
    { 
    for ($i=1; $i<=$rows->length ; $i++) 
    { 
     //echo($rows[$i]->getElementsByTagname('th')); 
     $cols = $rows->item($i)->getElementsByTagname('td'); 
     for ($j=0; $j <$cols->length ; $j++) 
     { 
      //echo($cols[$j]->nodeValue); 
      $input_lines = $cols[$j]->nodeValue; 
      $input_lines = preg_replace("/\D/", "", $input_lines); 
      echo $input_lines; 
      echo"<br><br>"; 

     }  
     } 
    } 

Fatal error: Call to a member function getElementsByTagname() on null

Answer 1

getElementsByTagName可能返回NULL（acording到文檔here），所以你需要檢查不空變量的方法：

$cols = $rows->item($i) 
if(!null($cols)){ 
    $cols = $cols->getElementsByTagname('td') 
} 
else { 
    throw new Exception("Element with name 'some name' was not found"); 
}